1. Technical Field of the Invention
This invention relates to telecommunication systems and, more particularly, to a volume-based system and method of monitoring and reporting accounting data in Internet Protocol (IP)-based telecommunications networks.
2. Description of Related Art
Prepaid telecommunication services are well-known. However, the emergence of packet data communications technology and the provision of packet data services raises new issues with respect to billing. Since data rates can vary greatly, conventional per minute charges are not preferred. Rather, charges should preferably be based on the volume of data (bytes/kilobytes) transferred to and from a given user engaged in a packet data session. It is therefore vitally important that the volume of data transferred for each user be monitored and reported as accurately as possible within each session.
It is particularly important to maintain an accurate count of the amount of data transferred to and from a Prepaid subscriber. Currently, the implementation of a prepaid solution for CDMA 2000 packet core networks is being investigated. The prepaid solution will introduce a prepaid service to CDMA 2000 users based on the volume of data transferred between each user and the IP network. However, existing procedures are unable to accurately report the amount of data transferred to and from mobile users during a handoff procedure, and are designed to report usage on the basis of the timed length of each call rather than the volume of data transferred.
The protocol utilized today to report accounting data from service nodes such as Packet Data Service Nodes (PDSNs) to accounting servers such as Authorization, Authentication, and Accounting (AAA) servers, is the RADIUS protocol. The RADIUS protocol utilizes Accounting-Request Interim messages today for interim accounting updates. These interim accounting updates are based on elapsed time rather than volume of data transferred, and provide cumulative information for the entire accounting session to the AAA Server. Thus, existing procedures are unable to properly control a Prepaid service that is based on the volume of data transferred in the case where a user exceeds his allotted volume.
Currently, with the RADIUS protocol, the Accounting-Request Interim messages are intermittently sent from the client PDSN to the AAA Server based on the value of an Accounting-Interim-Interval attribute returned from the AAA Server in a RADIUS Access-Accept message at the time of authentication. The time interval may also be set locally in the PDSN, and the interval returned from the AAA Server is then ignored. Obviously, the time interval only provides a way to perform accounting updates based on elapsed time. In addition, the AAA Server currently does not send a response to the PDSN in reply to these interim messages. The AAA Server only sends an Accounting-Response message to the PDSN in reply to an Accounting Request Start or Stop message. Therefore the Accounting-Request Interim messages are unidirectional from the PDSN to the AAA Server with regard to accounting. This is unacceptable for proper control of a Prepaid data session (i.e., to terminate the session when predetermined criteria are met).
The first revision of IS-835 introduced the concept of an accounting stop record trigger. An accounting stop record trigger is used to close an accounting session with an Accounting Stop message when the accounting record exceeds a configurable threshold size, or at any other threshold that an implementation dictates. If the applicable data session is continuing in the same PDSN, the Accounting Stop message is immediately followed by an Accounting Start message which begins another accounting session. The two accounting sessions are then correlated with a Correlation-ID.
For mobile users being handed off from an old (serving) PDSN to a new (target) PDSN, additional complexity is added to the accounting procedure. A proposal has been made to increase the speed at which handoff of a Mobile Station (MS) occurs between two PDSNs during Mobile IPv4 sessions. In the proposed fast handoff procedure, the MS is permitted to resume sending and receiving data before it has completed all of the necessary establishment procedures in the new PDSN. In the concept of Mobile IP, the MS maintains its IP address so it is always reachable, even if located in a different PDSN. Therefore, a tunnel is established between the old PDSN and the new PDSN, and any data packet destined for the MS during the handoff procedure is sent through the tunnel until the MS has successfully registered in the new PDSN, and the tunnel is torn down.
During the handoff, a release procedure from the radio access network dictates the release of all the connections to the MS from the old PDSN, and therefore dictates the closing of the accounting multi-session by sending a final Accounting Stop message from the old PDSN to the AAA Server. The new PDSN starts a new accounting session when several criteria are met: the MS sends a Mobile IP registration message, the MS is authenticated by the new PDSN, and the MS successfully registers with the Home Agent (HA). The new accounting session can be correlated with the old accounting session, but there is no way to account for any additional data that may have been sent to the MS through the tunnel during the handoff procedure. Additional packets may continue to be tunneled from the old PDSN to the new PDSN since the MS may still not have successfully registered with the HA in the new PDSN. Since tunneled traffic for the MS was sent or received after the accounting session was terminated in the old PDSN and prior to opening a new accounting session in the new PDSN, this traffic is not currently accounted for. The volume of data transferred needs to be considered for accounting purposes. For Prepaid users it is particularly important to maintain accurate accounting data in relation to their volume usage since this is the basis on which they are charged, and additional volume is purchased.
In order to overcome the disadvantage of existing solutions, it would be advantageous to have a system and method of monitoring and reporting accounting data in IP-based telecommunications networks that is based on volume, and accurately tracks the amount of data transferred during the handoff of an MS. The present invention provides such a system and method.